Signaling system



H. J. FISHER SIGNALING SYSTEM Filed Dec. 5, 1923 H/g/v Defec/or Frequmcy Amplifier Fl/fer Patented Jan.13,1925 i UNITED,- STATES;

I warn PATENT carton.

IIARoLn J. new, or JERSEY CITY, NEW JERsEY, ,ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, or NEW YORK, N. Y., A CORPORATION or NEW YORK.

SIGNALING SYSTEM.

Application filed December 5, 1923., Serial No. 678,662.

To all whom it may concern:

Be it known that I, HAROLD J. FISHER, a citizen of the United States of America, residing at Jersey Citiy, in the county of Hudson and State of ew Jersey, have invented certain new and useful Improvements in Signaling Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to a signaling system, and more particularly, to an arrangement in which telegraph signals transmitted as a plurality of modulations ofa single carrier wave may be received at a distant station substantially free from interference due to random disturbances such as static discharges.

It has heretofore been proposed to provide a radio telegraph system in whicha plurality of different frequency waves are used to efiect marking signals and a plurality of other waves of different frequencies are used to produce spacing signals.

In the arrangement hitherto proposed a carrier wave is modulated by a current of one frequency to produce a plurality of different carrier frequencies which are used to identify mar-kin signals and the same carrier wave is mo ulated by a current of different frequency to produce a plurality of other waves of different carrier frequencies which are employed to identify spaces.= In both cases the unmodulated carriercomponent is suppressed. At the receiving station the incoming waves are combined with locally generated oscillations to produce currents of frequencies different from the modulating frequencies, but which correspond thereto. These currents are separately selected and detected or rectified. The currents corresponding to the marking wave trains are each used to energize one winding of a set of windings of a polarized relay and each of the currents corresponding to the spacing wave trains is supplied to one winding of a second set of windings of the polarized relay. The relay is so designed that markin is only effectedwhen all the windings 0 one set are energized and spaces are indicated only when all the windings of the other set are energized,

whereby the polarized relay is positively.

actuated in two directions alternately to control the operation of a signal indicator. Static discharges incident upon the antenna windings of the relay, w ereby will produce oscillations determined by the natural period of the circuit. These oscillations when combined with the local oscillations will produce current impulses in all of the windings constitutin the two sets of a balanced condition will be produced with reference to the .relay armature and hence no effect, due to these impulses, will be produced in the signal indicating circuit. This receiving arrangement, therefore, requires a local oscillator, and also a selective circuit, rectifier, and relay winding for each of the incoming waves, in order that marking and spacing signals may be received and static interference eliminated.

The present invention provides an arrangement in which a carrier wave is mod-' ulated by two different frequencies and the modulated and unmodulated components are transmitted to a distant station at which the corresponding components arecombined to produce currents of themodulating frequencies which are selected, detected, or rectified and used to energize separate windings of a polarizing relay. In this arrangement the current of one frequency produced by detection is adapted to positively actuate the armature of the relay in one direction to indicate marking signals and similarly the produced current of the other frequency is adapted to positively actuate the armature of the relay in the opposite direction to-indicate spaces. Current impulses resulting from static discharges incident upon the antenna, will, in general, be simultaneously supplied to both windings of the polarizing relay and hence will not produce any effect upon the armature of the relay.

In accordance with this invention a controller is adapted to supply the unmodulated and modulated components of a carrier wave modulated with current of one fre quency to an antenna and then the unmodulated and modulated components same fre-' of a carrier wave of the quency modulated by a current of a different frequency to the antenna. At the receiving station the first group of carrier and side frequency components are combined in a detector to yield current of the first modulating frequency which is selected,

rectified and used to energize one winding of a differential relay and then the second group of carrier and side frequency components are combined in the same "detector to yield current of the second modulating fre uency which is selected, rectified, and use to energize the other winding of the differential relay. In this manner the relay is positivel operated; first in one direction to close a c rcuit including a marking device upon t 0 the relay to be simultaneously and equal and then in the opposite direction to open this circuit to return the marking device to spacingl position. Static discharges incident e antenna will cause both windin s Y energized and no effect due to these impulses will be produced inthe indicator circuit. The foregoing is given for the purpose of briefly and in a general way describing one practical embodiment by means of which the objects of this invention may be fulfilled. v

One object of this invention is to provide a radio telegraph system embodying a simple arrangement in which the signal impulses are used to positively operate an indicator while impulses due to random interference such as static are neutralized in their effect upon the indicator.

/For a complete understanding of this invention reference may be made to the following specification read in conjunction with the attached drawing in which the single figure illustrates a system embodying the invention.

In the drawing there is shown a transmission station T comprising an anteuna' circuit including a radiating conductor 1, an inductance 2 and an adjustable condenser 3 connected to ground at 4. An arrange-.

ment 5 for producing a carrier wave modulated by either one of two diflerent frequency currents, under the control of a key .6, is connected to the antenna circuit.

Any well known arrangement for supplying a carrier wave modulated by two currentsof diiferent frequencies may be used at the transmission station. By way of example, there is shown a transmission system which is similar to that described in U. S.v

Patent 1,349,729, August 17, 1920 to E. L. Nelson. It is specifically contemplated that the system of that patent may be used in cooperation with the arrangements herein disclosed in accomplishing the objects of the present invention.

Briefly described, this system is adapted to supply a carrier wave C modulated by a current of one frequency S to the antenna when the key 6 is open, and to supply a carrier wave C modulated by a current of different frequency S when the key 6 is closed. In both cases the side frequencies and the carrier components are radiated.

At the receiving station B there is shown an antenna circuit 7 inductively coupled to an amplifierB for supplying amplified radio irequency waves to a detector 9. The output of the detector includes two selective filter circuits 10 and 11 but obviously highly selective and are respective y selective of the different modulating currents of frequencies S andS;. The lelective circuits are separately coupled by coils 12 andi13 to the input circuits 0 r tifyin circuits consistin of devices 14- arid 15 an their associated ements. The output circuit of the device 14includesa windmg 16 of a polarized relay and similarly a winding 17 of the polarizedrelayis included in the output circuit of the device 15.

Polarizing potential is impressed upon the grid or control elements 0f the devices 14 and 15 by a common source 18 and space current is supplied thereto by the source 19. By maintaining a balanc ed relation in the circuits of the devices '14 and 15 equal currents will be supplied to .the windings 16- and 17. The armature 20 of the polarized relay is included in a circuit 21 which includes a relay 22. This relay 22 may bean ordinary telegraph sounder or the control winding of any Well known markingvdevice.

With the key 6 in the position shown, an unmodulated carrier component of frefrequency C and two side frequencies C-l-S and C-S will be supplied to and radiated from the antenna 1. At the receiving'station R the incoming unmodu lated and modulated components will be amplified by the device 8 and combined in the device 9 to produce a current of the modulating frequency S. The selective means 10 being resonant to current of the frequency S, this current will flow through the primary winding of the coil 12. The result of this is that the more strongly the. input circuit of the device 14 is excited by the waves impressed upon the secondary winding of the coil 12 the greater will be the average value of space current through the winding 16. The increased current flowing through the device 14 and its output circuit including the winding 16 of the polarized relay actuates hev relay armature 20 to open the circuit 21 asshown.

When the key 6 engages its contact, a carrier wave modulated by current of frebalanced detectingfor recl quency S will be supplied .to, and radiincreased energization of the secondary coil 13 will cause increased space current to fiow through the output circuit of the device includin the winding 17 of the polarized relay ant its armature will be actuated to com lets the circuit 21 and energize the Win ing 22 of the sounder or marking device.

By providing a relay which requires a large current unbalance to move its armature from one position to another, as by using an armature having large inert-1a, the relay will be more )ositive in operation and the liability of faise signaling will be reduced. v

When static discharges of certain frequencies are incident upon the antenna, oscillations may be set up therein, and current will flow simultaneousl through both the iesonant circuits 10 an 11. Both detectors 14 and 15 will be substantially equally affected, and a substantially equally increased s ace current will tend to flow s1- multaneously through the windings 16 and 17. y v

If the amplitudes of these currents are substantially equal the balanced condition of the detector system will not be disturbed and hence the olarized relay will not operate. Again, i? the difierence in the amplitudes of the currents flowing through windings 1.6 and 17- is less than that required to actuate the relay no signaling actuation will result. Thus, by pro erly desi ning the re- (-eiving circuit, inclu ing a be anced detector system adapted to control the flow of currents of large amplitude and utilizin a relay requiring acurrent of considera le amplitude to actuate its armature, it is possible to provide an arran ement in which the liability of false signalin due to static discharges, is greatly reduce From the be apparent iat this invention provides a simple arran ement for radio telegraph signalin in whicha'carrier wave modulated by two iflerent frequency currents may be used to positively actuate means for identifying marking and spacing signals.

The receiving circuit is herein described as including a high frequency amplifier, but this is not an essential element of the invention. 7

While a particular arrangement and certain specific details have been described for the purpose of completely and clearly dis. closing the nature of the present invention, it is to be understood that thisinvention is not limited thereto, but only by the scope .nals, producing preceding description it will t currents, separately selecting said modulating currents, utilizin one of said modulating currents to identify marking signals, using the other of said modulating currents to indicate spacing signals, and using the para-- sitic currents to produce substantially equal and opposing forces tending to produce marking and spacing signals.

2. The method of reducing random intcr fcrenco effects which comprises producin" a carrier wave alternately modulated at di ferent frequencies, transmitting the unmodulated carrier and the side frequency in both cases, and at a receiving station combining the corresponding components to produce currents ofsaid modulating frequencies, separately selecting said currents, utilizing one of said currents to ositively produce marking signals, using t e other of said currents to positively produce spacing sigcurrents by random 1nterference and using said last mentioned currents to tend to simultaneously produce opposing and neutralizing marking and spacing forces.

3. In a. si naling system means for transmittin in a ternation a carrier wave modulated by currents of difierent fre uencies and, at a receivin station, means or producmg currents o the modulating fre uencies, means 'for selecting said pro uced currents, means actuated in one direction by one of said currents to identify marking signals, means actuated in an opposite direction by the other ofv said currents to identify spacing signals, said two last mentioned means being simultaneously supplied with currents due to random inference such as static discharges.

'4. In a signaling system means to trans mit a carrier wave alternately modulated at different frequencies and, at a receiving station, means for producing currents of the modulating frequencies, means for selecting said currents, a marking circuit, means a1- terna-tely controlled by one of said modulating currents to positively complete said marking circuit, and by the other of said modulating currents to positively 0 en said marking circuit, said last mentione means being controlled by currents due" to random disturbances such as static discharges in a manner tending to simultaneously energize the circuit opening and closing control means.

5. In a signaling system means to transmit a carrier wavealternately modulated at different frequencies and, at a receiving station, means for producing currents of the modulating frequencies, a sounder circuit,

a balanced detector, means energized b one of said currents to control one side 0 said balanced detector to complete said sounder circuit and energized by the-other of said currents to control the other side of said detector to open said sounder circuit, said detectors being jointly controlled by currents due-to random disturbances such as static discharges to prevent actuation of the sounder circuit control means.

6. In a. signaling .system means to transmit a carrier wave alternately modulated at different frequencies and, at a receiving station, means for producing currents of the modulating frequencies, a marking circuit, balanced detectors, a polarized relay having one winding associated with one of the bulaneed detectors and a second winding associated with the other of said detectors, means energized by one of said currents for controlling one of said detectors to energize its associated relay winding, means energlzed by the other of said currents for controlling the other detector to energize its associated relay winding, said means being 2 jointly energized by currents due tcrrandom interference to control both detectors, whereby both' windings of the relay are jointly energized. a

In witness whereof, I hereunto subscribe my name this 27th day of November, A. D.

- HAROLD FISHER. 

